The present invention concerns new compounds containing in the same molecule two functional groups, which can give rise to radicals by a photochemical process. The compounds are suitable as polymerisation photoinitiators in photopolymerisable formulations containing ethylenic unsaturated systems.
Known photoinitiators contain in the molecule a functional group, which can give rise to radicals by excitation by an electromagnetic radiation, generally an UV radiation. These compounds are reported, for instance, in U.S. Pat. No. 3,715,293, DE 2722264, EP 161463, EP 3002, EP 88050, EP 284561, EP 192967, EP 850253. They are commonly used in polymerisation of ethylenic unsaturated systems. When pigmented systems are involved, such as in printing inks, the irradiating light cannot fully penetrate into the layer due to reflection and absorption of the pigment in the formulation. To obtain a good polymerization degree both at the surface level and in the inner layers of an ink, i.e. the so called surface and through cure of an ink, it is common practice to prepare formulations containing both a photoinitiator with a maximum UV absorption in the region of 250 nm and a photoinitiator with a significant absorption in the region above 300 nm. In fact above 300 nm most pigments have minimum in absorption and reflection (optical window) allowing the penetration of the light. The combination of the two kind of photoinitiators allows both surface and through cure of the formulation.
We have now surprisingly discovered the subject of the present invention, namely that molecules containing in their structure two different active moieties, both suitable to give rise to radicals, display high activity as photoinitiators, in particular in pigmented systems. The molecules can develop surprising synergies in comparison with the combined use of two photoinitiators containing each only one of the corresponding photoactive groups.
Moreover the absence in the molecule of functional groups that release volatile, odorous products by photolysis, improves the safety in the working environment, limiting the presence of volatile substances during the photopolymerisation stages in industrial processes.
Molecules generally used for the above mentioned purposes are based on two phenyl groups linked together, each substituted by a photochemically active ketonic moiety. The aromatic groups can be further substituted by non-photochemically active moieties. Among these molecules those based on two phenyl rings connected together through a suitable linking group and substituted in positions 4,4xe2x80x2 by two ketonic moieties are the most suitable.
Therefore the present invention deals with compounds having formula (I) 
wherein
X1 and X2 are different
X1 is a group 
wherein
R1 and R2, each independently, are xe2x80x94H or C1-C12 linear or branched or cyclic alkyl chain, aryl, alkylaryl groups.
Z1 is xe2x80x94SO2R3, xe2x80x94NR4R5, xe2x80x94OR1, halogen.
R3 is: C1-C12 linear or branched alkyl chain, or: 
wherein
R6, R7, R8, R9 and R10 each independently, are xe2x80x94H or C1-C12 linear or branched or cyclic alkyl chain, aryl group,xe2x80x94OR11, -alcohoxyhydroxy, hydroxyalkylthio-, xe2x80x94SR11, xe2x80x94Sxe2x95x90OR12, xe2x80x94SO2R13, xe2x80x94Cxe2x95x90OR14, xe2x80x94NR15R16, CN, -halogen;,
R11 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group,
R12 is C1-C12 linear or branched alkyl chain, aryl group,
R13 is C1-C12 linear or branched alkyl chain, aryl group, xe2x80x94OH, xe2x80x94OAlkyl, xe2x80x94NH2, xe2x80x94NHAlkyl, xe2x80x94N(Alkyl)2, xe2x80x94NH Aryl, xe2x80x94N(Aryl)2,
R14 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, xe2x80x94OH, xe2x80x94OAlkyl, xe2x80x94NH2, xe2x80x94NHAlkyl, xe2x80x94N(Alkyl)2, xe2x80x94NH Aryl, xe2x80x94N(Aryl)2,
R15 and R16, each independently, are xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, COR1 or, if coincident, represent C2-C6 alkylene, C2-C6 oxa-, thia- or aza-alkylene,
R4 and R5, each independently, are xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, COR1 or, if coincident, represent C2-C6 alkylene, C2-C6 oxa-, thia- or aza-alkylene,
X2 is a group 
wherein
R6, R7, R8, R9, R10 have the meaning already stated or X2 is a group 
wherein
R1, R2 have the meaning already stated, and Z2 has the same meaning of Z1 provided that X2 is different from X1 
Y is: single bond, C1-C12 linear or branched alkylene, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94,  greater than Sxe2x95x90O,  greater than SO2, xe2x80x94NR17xe2x80x94,
wherein
R17 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, CO R1.
The present invention further relates to photopolymerisable formulations containing at least one of the components of formula (I).
Preferred photonitiators for pigmented systems are compounds of formula (I) in which:
Y is: single bond, xe2x80x94Sxe2x80x94, xe2x80x94NR17xe2x80x94, wherein R17 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, CO R1.
Particularly preferred as photoinitiators for pigmented systems are compounds of formula (I) in which:
X1 is a group 
wherein
R1 and R2, each independently , are xe2x80x94H or C1-C12 linear or branched or cyclic alkyl chain, aryl, alkylaryl groups.
Z1 is xe2x80x94SO2R3, xe2x80x94NR4R5, halogen
R3 is: C1-C12 linear or branched alkyl chain, or: 
wherein
R6, R7, R8, R9 and R10 each independently, are xe2x80x94H or C1-C12 linear or branched or cyclic alkyl chain;
R4 and R5 are each independently, H, C1-C12 linear or branched alkyl, aryl, COR1 or, if coincident, represent C2-C6 alkylene, C2-C6 oxa-, thia- or aza-alkylene,
X2 is a group 
wherein
R6, R7, R8, R9 and R10 each independently, are xe2x80x94H or C1-C12 linear or branched or cyclic alkyl chain, aryl group,xe2x80x94OR11, -alcohoxyhydroxy, hydroxyalkylthio-, xe2x80x94SR11, xe2x80x94Sxe2x95x90OR12, xe2x80x94SO2R13, xe2x80x94Cxe2x95x90OR14, xe2x80x94NR15R16, CN, -halogen;
R11 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group,
R12 is C1-C12 linear or branched alkyl chain, aryl group,
R13 is C1-C12 linear or branched alkyl chain, aryl group, xe2x80x94OH, xe2x80x94OAlkyl, xe2x80x94NH2, xe2x80x94NHAlkyl, xe2x80x94N(Alkyl)2, xe2x80x94NH Aryl, xe2x80x94N(Aryl)2,
R14 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, xe2x80x94OH, xe2x80x94OAlkyl, xe2x80x94NH2, xe2x80x94NHAlkyl, xe2x80x94N(Alkyl)2, xe2x80x94NH Aryl, xe2x80x94N(Aryl)2,
R15 and R16, each independently, are xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, COR1 or, if coincident, represent C2-C6 alkylene, C2-C6 oxa-, thia- or aza-alkylene,
or a group 
wherein
R1 and R2, are defined above.
Z2 is xe2x80x94SO2R3, xe2x80x94NR4R5, xe2x80x94OR1, halogen wherein R1, R3, R4 and R5, are defined above
Y is: xe2x80x94Sxe2x80x94, xe2x80x94NR7xe2x80x94, wherein R17 is xe2x80x94H, C1-C12 linear or branched alkyl chain, aryl group, CO R1.
Examples of compounds suitable for the application according to the present invention are the following, however the present invention is by no means limited thereto:
4-benzoyl-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (1)
4-(4-methylbenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (2)
4-(4-phenylbenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (3)
4-(4-fluorobenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (4)
4-(2-methylbenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (5)
4-benzoyl-4xe2x80x2-(2-bromo-1-propanoyl)diphenylsulfide (6)
4-(2,4,6-trimethylbenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (7)
4-(2-hydroxybenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (8)
4-(4-methoxybenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (9)
4-(4-cianobenzoyl)-4xe2x80x2-(2-bromo-2-methyl-1-propanoyl)diphenylsulfide (10)
4-benzoyl-4xe2x80x2-(2-bromo-2-phenyl-1-ethanoyl)diphenylsulfide (11)
4-benzoyl-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (12)
4-(4-methylbenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (13)
4-benzoyl-4xe2x80x2-phenylacetyl-diphenylsulfide (14)
4-benzoyl-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-phenyl-1-ethanoyl]diphenylsulfide (15)
4-(4-phenylbenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (16)
4-(4-fluorobenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (17)
4-(4-morpholinobenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (18)
4-(2-methylbenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (19)
4-benzoyl-4xe2x80x2-[2-(4-methylphenylsulfonyl)-1-propanoyl]diphenylsulfide (20)
4-(4-methoxybenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (21)
4-(2,4,6-trimethylbenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (22)
4-(2-hydroxybenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (23)
4-(4-cianobenzoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (24)
4-(4-mercaptobenzoyl )-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (25)
4-benzoyl-4xe2x80x2-(2-methyl-2-morpholino-1-propanoyl)diphenylsulfide (26)
4-(2-methyl-2-morpholino-1propanoyl)-4xe2x80x2-(2-hydroxy-2-methyl-1-propanoyl) diphenylsulfide (27)
4-(2-methyl-2-hydroxy-1-propanoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (28)
4-[4-(2-hydroxy-1-ethoxy)-benzoyl-]4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (29)
4-(2-methyl-2-morpholino-1-propanoyl)-4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (30)
4-[4-(2-hydroxyethylthio)-benzoyl-]4xe2x80x2-[2-(4-methylphenylsulfonyl)-2-methyl-1-propanoyl]diphenylsulfide (31)
According to the present invention, pigmented photopolymerisable formulations contain at least one of the following compounds: compound (12), compound (13), compound (15), compound (16), compound (17), compound (18), compound,(19), compound (20), compound (21), compound (22), compound (23), compound (24), compound (25), compound (26), compound (27), compound (28), compound (29), compound (30), compound (31).
According to the present invention, compounds having formula (I) are used as photoinitiators in photopolymerisable systems containing reactive monomers and oligomers. The words xe2x80x9cphotopolymerisable systemxe2x80x9d or xe2x80x9cphotopolymerisable formulationxe2x80x9d means in the present text a mixture of photopolymerisable or cross-linkable monomers and oligomers, at least one photoinitiator, fillers pigments, dispersants, and other additives of general use. The expression xe2x80x9cphotopolymerisationxe2x80x9d is meant in broad sense and includes, for instance, further polymerisation or cross-linking of polymeric material, for instance of prepolymers, homopolymerisation and copolymerisation of simple monomers, and combination of these reactions. Suitable monomers which can be used in the system described in the present invention, comprise: acrylonitrile, acrylamide and their derivatives; vinyl ethers; N-vinylpyrrolidone; mono and polyfunctional allyl ethers, such as trimethylolpropandiallyl ether; styrenes and alpha-methylstyrenes; esters of acrylic and methacrylic acid with aliphatic alcohols, glycols, polyhydroxylated compounds, such as pentaerythritol or trimethylolpropane or amminoalcohols; esters of vinyl alcohol with aliphatic or acrylic acids; derivatives of fumaric and maleic acids.
Reactive oligomers, suitable for the present invention, include polyesters, polyacrylates, polyurethanes, epoxy resins, polyethers containing acrylic, fumaric or maleic functionalities. Pigments used comprise inorganic pigments such as titanium dioxide and xe2x80x9cCarbon blackxe2x80x9d, organic pigments based on azo, phtalocyanine, antraquinone etc.
Compounds of formula (I) of the present invention act as photoinitiators and may be used alone or in combination with other photoinitiators such as benzophenone, benzyldimethylketale, alpha-hydroxyketones, benzoin ethers, alpha-amminoketones etc. Particularly advantageous turns out the combination with tertiary amines, which increase the cross-linking rate and reduce oxygen inhibiting effects such as triethylamine, N-methyldiethanolamine, N,N-dimethylethanolamine, esters of p-dimethylaminobenzoic acid. For pigmented systems turns out particularly advantageous the use of sensitising substances or co-initiators, such as thioxanthones and their derivatives.
In addition to the compounds having formula (I), many components may be included in the photopolymerisable system, such as thermal stabilisers, sensitisers, photo-oxidation stabilisers such as sterically hindered amines, antioxidants, atmospheric oxygen exclusion agents, thermal generators of radicals such as organic and inorganic peroxides, peresters, hydroperoxydes, benzopinacols, azoderivatives such as azoisobutyronitrile, metallic compounds such as cobalt (II) salts, manganese, antifoam, fillers, dyes, glass and carbon fibres, thixotropic agents. Other components are constituted by not-photopolymerisable polymers, present as chemically inert substances, such as nitrocellulose, polyacrylic esters, polyolefines, etc., or cross-linkable polymers by alternative routes such as peroxides and atmospheric oxygen or by acid catalysis or thermal activation, such as polyisocyanates, urea, melamine or epoxy resins. Such photopolymerisable systems may be either of transparent or pigmented kind, and they are used in printing, graphic arts, plastic materials, metals, wood, glass etc. fields. It is noteworthy their use in the inks field, above all those having high pigmentation level: in this application pigments are present in amounts ranging from 10 to 60% by weight, and preferably between 15 and 40%.
Compounds having formula (I) are generally used in a quantity of from 0.01% to 20% by weight, preferably from 0.5% to 5% by weight, based on the composition. They show great dispersability in photopolymerisable systems, to which they give high photochemical reactivity and light stability.
Examples of light sources used for photopolymerisation are high, medium or low-pressure mercury-vapour lamps, superactinic lamps or excimer lamps, with emission bands in the UV-vis region up to 400 nm. Among possible light sources even sunlight or other artificial sources, such as xenon, tungsten lamps, and laser sources are included. In cross-linking of inks containing titanium dioxide, xe2x80x9cdopedxe2x80x9d lamps with a particularly high emission between 350 and 450 nm are preferably used.
In preparation of inks, the above mentioned compositions containing pigments are ground up to the obtainment of a granulometry comprised between 0.1 and 2 xcexcm and preferably lower than 1 xcexcm in a three cylinders refiner. Such grinding may be carried out either before or after the addition of a photoinitiator and co-initiator mixture, wherein the photoinitiator is contained in an amount of from 30% to 70% by weight. Finally the polymerisation is obtained by known methods, by irradiation at the suitable wavelength range.
The preparation of the above mentioned photoinitiators, having formula (I), can be performed by several methods described in scientific and patent literature and well known to those skilled in the art.
In particular compounds having formula (I), in which Z1=xe2x80x94SO2R3 or halogen and R3 has the above meaning already, X2=
wherein R6, R7, R8, R9, R10 have the above meaning, are preferably prepared according the following process comprising the following steps:
a) reacting an arylacylchloride of formula (II) 
wherein R6, R7, R8, R9, R10 have the meaning above defined with the exclusion of one of them being=xe2x80x94NR15R16, with the compound of formula (III) 
wherein Y has the above mentioned meaning in the presence of a Lewis acid such as, for instance, AlCl3, at temperature comprised between 5xc2x0 C. and 25xc2x0 C., thereby obtaining the compound (IV) 
b) reacting the intermediate (IV) with a dialkylhaloacetyl halogenide of formula (V): 
wherein R1 and R2 have the above meaning, except for R1 or R2=H and R1 or R2=Aryl; X=halogen, preferably Cl or Br, in the presence of a Lewis acid such as, for instance, AlCl3, at temperature ranging from 5xc2x0 C. and 25xc2x0 C., to obtain compound (IA) 
or
b1) reacting intermediate (IV) with a dialkylacetyl halogenide of formula (VI): 
wherein R1 or R2=H and R2 or R1=Aryl and X=halogen in the presence of a Lewis acid such as, for instance, AlCl3, at temperature comprised between 5xc2x0 C. and 25xc2x0 C., thereby obtaining the intermediate of formula (VII) 
which is further halogenated, preferably brominated or chlorinated thereby obtaining intermediate (IA) wherein R1 or R2=H and R2 or R1=Aryl and X=halogen.
c) reacting the intermediate of formula (IA) coming from step (b) or (b1), with the sodium sulfinate derivative of formula R3SO2xe2x88x92Na+, wherein R3 has the significance already stated, in an organic solvent, preferably an alcohol or an amide, at a temperature of between 60xc2x0 C. and 120xc2x0 C. thereby obtaining the compound of formula (IB) 
d) optionally reacting derivative (IB) wherein R8=halogen, with an amine of formula NHR15R16 thereby obtaining compound of formula (IC) 
Alternatively in the above-mentioned process, steps (a) and (b) can be carried out at the same time.
In particular the preferred process to synthesise compounds of formula (I) wherein
X2 is a group 
wherein R6, R7, R8, R9, R10 have the above meaning and X1 is a group 
wherein Z1 is NR4R5, besides steps (a), (b) or (b1) above mentioned, includes the following steps:
cxe2x80x2) reacting the compound of formula (IA) obtained from (b) or (b1) with sodium methylate in methanol under reflux to obtain the intermediate of formula (VIII): 
dxe2x80x2) The intermediate of formula (VIII) reacts with the amine of formula HNR4R5 in anhydrous acetonitrile to obtain the compound of formula (I).
We report the following examples for illustrative but not limitative purposes of the preparation of the compounds of the present invention and of the photopolymerisable formulations.